Relationship to Humans:
Some fruit fly homeotic genes have mouse and human orthologs that also act as developmental genes. These orthologous genes control the position of the embroys in both flies and humans even though the structures produced at each place have differed. Since these genes have stayed constant over millions of years, their functions must have been advantageous in many different environmental conditions. One gene in humans, called the Sonic hedgehog (Shh) gene, is orthologous to the hedgehog gene in Drosophlia. Both genes activate a signaling pathway involved in different parts of development in each organism. The formation of anterior and posterior axes are one of the developmental processes that is similar in both human and Drosophila embryos.
Habitat and Niche: The common fruit fly has been introduced to almost all temperate regions of the world, but native habitats include temperate, tropical, and terrestrial regions. Aspects that limit where Drosophilia melanogaster can thrive are temperature and availability of water because this species lives in moist environments. (2)
Predator Avoidance: Fruits flies often have sensory modalities (reactions to stimulus) to predators. They will favor finding shelter or will fly away when they detect a known predator is in their presence (6). Fruit flies also have extremely fast life cycles and continually reproduce. The sheer number of fruit flies in a population is another way of avoiding predators because there is no way a predator can get to them all. The life cycle of a fruit fly from egg to adult is generally just 8 days (7).
Nutrient Acquisition:
Drosophila ingest their food through an oral cavity. They commonly feed on fruits and other decaying organic materials to obtain their nutrition.
The mouth of an insect has 4 parts: the labrum, mandibles, maxillae, and labium. The labrum moves longitudinally and is often called the upper lip. The mandibles are like jaws and move at 90o angles to the body, used for biting and chewing. The maxillae are paired structures, and they move at right angles to the body as well, possessing segmented palps (structures usually focused on touch and taste senses). Lastly, the labium, or lower lip, also moves longitudinally and harnesses segmented palps. There are 2 functional groups of mouth parts in insects: mandibulate and haustellate. Mandibulates are used for chewing while haustellate mouth parts are used for sucking or sponging (14).
Reproduction and Life Cycle:
Drosophila that emerge from pupation in a piece of rotting fruit are ready to mate in approximately eight hours and have very complex courtship rituals. Chasing after the female fruit fly, the male will also tap her body with his forelegs. Then, if the female does not flee, the male will then extend a wing and vibrate it to make a song. Lastly, if the female continues not to run away, the male fruit fly will lick her genitals and then attempt to copulate.
A fruitless (fru) gene was found in Drosophila that effects sexual behavior in males. This gene is selectively expressed in the cells in the nervous system of the fly which are involved in sexual differentiation and sexual behavior. In addition, this gene product is a transcription factor responsible for the expression of many other genes, and modifications to those genes can also alter other aspects of the fly's behavior.
The reproduction in Drosophila is rather rapid. A single pair of Drosophila can produce hundreds of offspring within a couple of weeks, and the offspring become sexually mature within just one week. Drosophila, like almost all other insects, lays eggs. The eggs are placed on fruit, and hatch into fly larvae (maggots), which instantly start consuming the fruit on which they were laid. (8)
Growth and Development:
The process of going from fertilized egg to adult takes about two weeks in Drosophila. During fertilization, mitosis occurs rapidly in the Drosophila, but cytokinesis only occurs for the first time at the 13th division cycle. Therefore, the embryo is not multicellular, but multinucleate until the 13th division cycle. Drosophila embryos are like many other organism's embryos such that they are characterized by an uneven distribution of cytoplasmic determinants. These are made from maternal effect genes which determine the anterior and posterior ends of the egg. The Bicoid maternal effect gene's mRNA is translated to produce a Bicoid protein, which creates a concentration gradient when it diffuses away from the anterior axis. Acting as a transcription factor, the Bicoid protein stimulates transcription of the hunchback gene (making a hunchback protein gradient). Another maternal effect gene, called Nanos, does the similar actions except with Nanos protein in the posterior axis of the egg. The Nanos protein inhibits translation of the hunchback mRNA, therefore preventing accumulation of the hunchback protein. Both Bicoid and Nanos proteins create a gradient of the hunchback protein, determining the posterior and anterior sides of the embryo. This occurs before fertilization and during the multinucleate stage, which lasts a few hours. After the anterior and posterior ends have been determined, segments of the fruit fly are formed. This occurs during the larval stage, determined by proteins coded for by genes known as segmentation genes. Gap genes, pair rule genes, and segment polarity genes also assist development of segments in the fly. Hox genes help assign specificity to cells in order for the segments to have the correct organs in the right places.
The egg hatches into a larva (about 24 hours after the egg has been fertilized), then a pupa, and then an adult fly.
Integument: The insect integument is made of a monolayer of epidermal (or hypodermal) cells and most of the signaling pathways that are responsible for epidermis morphogenesis therefore take place in a two dimensional space. The exoskeleton of a fruit fly is made of chitin, a polysaccharide comprised of N-acetyl-glucosamine. Movement:
Fruit flies have wings that allow them to fly, but they also have leg structures. However, if a protein called Ultrabithorax binds a certain way during development, a fly could produce halteres instead of full hind wings. Halteres maintain equilibrium during flight, also called balancers. (11)
Sensing the Environment: Fruit flies have a gustatory receptor which senses heat instead of taste or smell. This senses external temperatures and sends signals for quick adjustments to be made in order for the fly to stay within its "Goldilocks Zone", also known as Gr28b (9). Fruit Flies have large compound eyes equipped with many ommatidium. Ommatidium are clusters of light-detecting cells that each recieve light at slightly different angles. This gives the fruit fly a wide range of vision, excellent close range eyesight and makes it very good at detecting movement.
Gas Exchange:
Insects have tubular channels called tracheae (singular trachea). Extending from external openings called spiracles inward to tissues throughout the body, these tubes end with air sacs similar to alveoli in humans. The spiracles are located on the sides of the abdomen and thorax, and these openings can close to decrease water loss. The spiracles attach to the tracheae which branch into smaller tubes known as tracheoles. The tracheoles end at the air sacs called air capillaries (where the gas exchange occurs). The large number of branching tubes makes up a large amount of surface area in insects, so air can diffuse into all the cells in the body.
Waste Removal:
Flies regurgitate and excrete waste through the anus onto any surface that they land on.
The digestive system, or alimentary canal, consists of the fore gut, mid gut, and hind gut. Malpighian tubules reside close to the junction of the mid gut and hind gut, working in conjunction with part of the hind gut to provide the primary site for excretion and aid in osmoregulation. These structures empty into the alimentary canal and remove nitrogenous wastes from the insect’s body (14).
Environmental Physiology:
Fruit flies cannot internally regulate body temperature, so behavioral thermoregulation allows them to maintain a stable body temperature within a set range. Their internal structures equilibrate to the temperature of the environment. Fruit flies lack short-term plasticity and prefer a stable temperature in the mid 20o C range (12). To regulate water intake and recognition, fruit flies have osmosensitive ion channels (ppk28) that facilitate both cellular and behavioral responses to water (13).
Internal Circulation:
Drosophilia has an open circulation system that has fluid flowing freely (4). The fluid is called hemolymph and contains copper, rather than iron which is in hemoglobin. Hemolymph is poor with oxygen, so the color of the hemolymph in a fruit fly is a greenish yellow.
Chemical Control:
In the larval stage of a fruit fly's life, the larva eats until it is too large for its exoskeleton. Then, endocrine cells in the fly's brain produces a hormone called prothoraciotropic hormone (PTTH), which is then released into the body. When the PTTH reaches the prothoracic gland, located in the thorax, it stimulates the gland to release ecdysone, a hormone that causes the larva to molt.
Another hormone called juvenile hormone (JH) controls whether the larva molts into a larger larva or into an adult fly. Throughout the fly's life, JH is constantly produced in the brain. When the larva gets older, the amount of JH produces decreases. A low enough amount of JH will cause the larva to progress to the adult stage.
Review Questions:
1. What do fruit flies and humans have in common and how could this help explain the evolution of humans?
2. What are the four major stages of the reproduction cycle? Which parts of the cycle are similar to the early stages in human development?
3. Explain what the Ultrabithorax protein has to do with movement.
Classification/Diagnostic Characteristics:
Domain:
Kingdom:Animalia
Phylum:Arthropoda
Class: Insecta
Order: Diptera
Family: Drosophilidae
Genus: Drosophila
Species:
Relationship to Humans:
Some fruit fly homeotic genes have mouse and human orthologs that also act as developmental genes. These orthologous genes control the position of the embroys in both flies and humans even though the structures produced at each place have differed. Since these genes have stayed constant over millions of years, their functions must have been advantageous in many different environmental conditions. One gene in humans, called the Sonic hedgehog (Shh) gene, is orthologous to the hedgehog gene in Drosophlia. Both genes activate a signaling pathway involved in different parts of development in each organism. The formation of anterior and posterior axes are one of the developmental processes that is similar in both human and Drosophila embryos.
Habitat and Niche:
The common fruit fly has been introduced to almost all temperate regions of the world, but native habitats include temperate, tropical, and terrestrial regions. Aspects that limit where Drosophilia melanogaster can thrive are temperature and availability of water because this species lives in moist environments. (2)
Predator Avoidance: Fruits flies often have sensory modalities (reactions to stimulus) to predators. They will favor finding shelter or will fly away when they detect a known predator is in their presence (6). Fruit flies also have extremely fast life cycles and continually reproduce. The sheer number of fruit flies in a population is another way of avoiding predators because there is no way a predator can get to them all. The life cycle of a fruit fly from egg to adult is generally just 8 days (7).
Nutrient Acquisition:
Drosophila ingest their food through an oral cavity. They commonly feed on fruits and other decaying organic materials to obtain their nutrition.
The mouth of an insect has 4 parts: the labrum, mandibles, maxillae, and labium. The labrum moves longitudinally and is often called the upper lip. The mandibles are like jaws and move at 90o angles to the body, used for biting and chewing. The maxillae are paired structures, and they move at right angles to the body as well, possessing segmented palps (structures usually focused on touch and taste senses). Lastly, the labium, or lower lip, also moves longitudinally and harnesses segmented palps. There are 2 functional groups of mouth parts in insects: mandibulate and haustellate. Mandibulates are used for chewing while haustellate mouth parts are used for sucking or sponging (14).
Reproduction and Life Cycle:
Drosophila that emerge from pupation in a piece of rotting fruit are ready to mate in approximately eight hours and have very complex courtship rituals. Chasing after the female fruit fly, the male will also tap her body with his forelegs. Then, if the female does not flee, the male will then extend a wing and vibrate it to make a song. Lastly, if the female continues not to run away, the male fruit fly will lick her genitals and then attempt to copulate.
A fruitless (fru) gene was found in Drosophila that effects sexual behavior in males. This gene is selectively expressed in the cells in the nervous system of the fly which are involved in sexual differentiation and sexual behavior. In addition, this gene product is a transcription factor responsible for the expression of many other genes, and modifications to those genes can also alter other aspects of the fly's behavior.
The reproduction in Drosophila is rather rapid. A single pair of Drosophila can produce hundreds of offspring within a couple of weeks, and the offspring become sexually mature within just one week. Drosophila, like almost all other insects, lays eggs. The eggs are placed on fruit, and hatch into fly larvae (maggots), which instantly start consuming the fruit on which they were laid. (8)
Growth and Development:
The process of going from fertilized egg to adult takes about two weeks in Drosophila. During fertilization, mitosis occurs rapidly in the Drosophila, but cytokinesis only occurs for the first time at the 13th division cycle. Therefore, the embryo is not multicellular, but multinucleate until the 13th division cycle. Drosophila embryos are like many other organism's embryos such that they are characterized by an uneven distribution of cytoplasmic determinants. These are made from maternal effect genes which determine the anterior and posterior ends of the egg. The Bicoid maternal effect gene's mRNA is translated to produce a Bicoid protein, which creates a concentration gradient when it diffuses away from the anterior axis. Acting as a transcription factor, the Bicoid protein stimulates transcription of the hunchback gene (making a hunchback protein gradient). Another maternal effect gene, called Nanos, does the similar actions except with Nanos protein in the posterior axis of the egg. The Nanos protein inhibits translation of the hunchback mRNA, therefore preventing accumulation of the hunchback protein. Both Bicoid and Nanos proteins create a gradient of the hunchback protein, determining the posterior and anterior sides of the embryo. This occurs before fertilization and during the multinucleate stage, which lasts a few hours. After the anterior and posterior ends have been determined, segments of the fruit fly are formed. This occurs during the larval stage, determined by proteins coded for by genes known as segmentation genes. Gap genes, pair rule genes, and segment polarity genes also assist development of segments in the fly. Hox genes help assign specificity to cells in order for the segments to have the correct organs in the right places.
The egg hatches into a larva (about 24 hours after the egg has been fertilized), then a pupa, and then an adult fly.
Integument:
The insect integument is made of a monolayer of epidermal (or hypodermal) cells and most of the signaling pathways that are responsible for epidermis morphogenesis therefore take place in a two dimensional space. The exoskeleton of a fruit fly is made of chitin, a polysaccharide comprised of N-acetyl-glucosamine.
Movement:
Fruit flies have wings that allow them to fly, but they also have leg structures. However, if a protein called Ultrabithorax binds a certain way during development, a fly could produce halteres instead of full hind wings. Halteres maintain equilibrium during flight, also called balancers.
Sensing the Environment:
Fruit flies have a gustatory receptor which senses heat instead of taste or smell. This senses external temperatures and sends signals for quick adjustments to be made in order for the fly to stay within its "Goldilocks Zone", also known as Gr28b (9).
Fruit Flies have large compound eyes equipped with many ommatidium. Ommatidium are clusters of light-detecting cells that each recieve light at slightly different angles. This gives the fruit fly a wide range of vision, excellent close range eyesight and makes it very good at detecting movement.
Gas Exchange:
Insects have tubular channels called tracheae (singular trachea). Extending from external openings called spiracles inward to tissues throughout the body, these tubes end with air sacs similar to alveoli in humans. The spiracles are located on the sides of the abdomen and thorax, and these openings can close to decrease water loss. The spiracles attach to the tracheae which branch into smaller tubes known as tracheoles. The tracheoles end at the air sacs called air capillaries (where the gas exchange occurs). The large number of branching tubes makes up a large amount of surface area in insects, so air can diffuse into all the cells in the body.
Waste Removal:
Flies regurgitate and excrete waste through the anus onto any surface that they land on.
The digestive system, or alimentary canal, consists of the fore gut, mid gut, and hind gut. Malpighian tubules reside close to the junction of the mid gut and hind gut, working in conjunction with part of the hind gut to provide the primary site for excretion and aid in osmoregulation. These structures empty into the alimentary canal and remove nitrogenous wastes from the insect’s body (14).
Environmental Physiology:
Fruit flies cannot internally regulate body temperature, so behavioral thermoregulation allows them to maintain a stable body temperature within a set range. Their internal structures equilibrate to the temperature of the environment. Fruit flies lack short-term plasticity and prefer a stable temperature in the mid 20o C range (12). To regulate water intake and recognition, fruit flies have osmosensitive ion channels (ppk28) that facilitate both cellular and behavioral responses to water (13).
Internal Circulation:
Drosophilia has an open circulation system that has fluid flowing freely (4). The fluid is called hemolymph and contains copper, rather than iron which is in hemoglobin. Hemolymph is poor with oxygen, so the color of the hemolymph in a fruit fly is a greenish yellow.
Chemical Control:
In the larval stage of a fruit fly's life, the larva eats until it is too large for its exoskeleton. Then, endocrine cells in the fly's brain produces a hormone called prothoraciotropic hormone (PTTH), which is then released into the body. When the PTTH reaches the prothoracic gland, located in the thorax, it stimulates the gland to release ecdysone, a hormone that causes the larva to molt.
Another hormone called juvenile hormone (JH) controls whether the larva molts into a larger larva or into an adult fly. Throughout the fly's life, JH is constantly produced in the brain. When the larva gets older, the amount of JH produces decreases. A low enough amount of JH will cause the larva to progress to the adult stage.
Review Questions:
1. What do fruit flies and humans have in common and how could this help explain the evolution of humans?
2. What are the four major stages of the reproduction cycle? Which parts of the cycle are similar to the early stages in human development?
3. Explain what the Ultrabithorax protein has to do with movement.
Sources:
1. http://animaldiversity.ummz.umich.edu/accounts/Drosophila/classification/
2. http://animaldiversity.ummz.umich.edu/site/accounts/information/Drosophila_melanogaster.html#habitat
3. http://whatcom.wsu.edu/ipm/swd/
4. https://www.boundless.com/biology/circulatory-system/facilitating-exchange-with-cells-throughout-the-body/open-and-closed-circulatory-systems/
5.http://www.google.com/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=1&ved=0CCkQFjAA&url=http%3A%2F%2Fwww.ijdb.ehu.es%2Fweb%2Fdescarga%2Fpaper%2F15272387&ei=QiSJUu6XDOjJsATNsoHoCQ&usg=AFQjCNGYfHQ-SRrvxPthuexnh7GHVic5tg
6. http://www.drosophila-conf.org/2012/abstracts/text/f70790.htm
7. http://insects.about.com/od/insectssociety/qt/Where-Do-Fruit-Flies-Come-From.htm
8. http://animaldiversity.ummz.umich.edu/accounts/Drosophila_melanogaster/#physical_description
9. http://www.redorbit.com/news/science/1112918664/fruit-flies-detect-temperature-taste-receptors-080813/
10. http://quest.nasa.gov/projects/flies/anatomy.html
11. http://www.transitionrig.com/insect.htm
12. http://genesdev.cshlp.org/content/24/21/2365.full
13. http://www.sdbonline.org/fly/genebrief/ppk28.htm
14. http://www.entomology.umn.edu/cues/4015/morpology/